Author: Publisher:
ISBN:
Category :
Languages : en
Pages : 60
Book Description
On the Effects of Pressure and Excess Gas Velocity on the Bubble Behaviour and Gas Flow Distribution in a Fluidized Bed
Author: The Effect of Particle Size on the Properties of Gas-fluidized Beds
Author: K. S. SutherlandPublisher:
ISBN:
Category : Bulk solids flow
Languages : en
Pages : 58
Book Description
The development of a continuous method for determining changes in particle size and particle size distribution in fluid-bed systems has been studied experimentally. Differential pressure measurements were employed to study the effects of solid particle size on the behavior of gas-fluidized beds. The relevant bed properties are briefly described and a review given of previous work on the study of fluidized-bed quality. It is shown that, within certain limitations, measurements of bed quality can be used to indicate changes in particle size. Gas-bubble velocities, while increasing in proportion to the square root of bubble diameter, are also shown to be dependent on particle size, increasing as the particle size decreases.
An Experimental Investigation of the Bubble Behaviour and Gas Flow Distribution in a Pressurized Fluidized Bed
Author: Fluid Dynamics of Turbulent Fluidized Beds for Geldart’s Group B Particles
Author: Tom WytrwatPublisher: Cuvillier Verlag
ISBN: 3736965710
Category : Technology & Engineering
Languages : en
Pages : 200
Book Description
An in-depth experimental study of the fluid dynamics of turbulent fluidized beds with particles of Geldart’s Group B was carried out. For this purpose, fluidization behavior was investigated in different fluidized bed plants having diameters in the range of 0.05 m to 1 m. Pressure fluctuation analysis has been used as an identification tool for the turbulent fluidized bed regime. Different fluidization conditions have been investigated by variation of the fluidized bed properties, the bed material properties, and the gas properties. Based on the measured data, a correlation predicting the transition velocity from bubbling to turbulent fluidization is introduced. To investigate the local flow structure, capacitance probe measurements have been carried out. Using this measurement technique, local solids concentrations and properties of rising bubbles have been determined and analyzed. Finally, an empiric fluid dynamic model was developed using the local measurement data. It is mainly based on capacitance probe measurements and shows high accuracy in comparison to pressure data.
An Experimental Investigation of the Bubble Behaviour and Gas Flow Distribution in a Presurized Fluidized Bed
Author: Per OlowsonFluidization
Author: J. F. DavidsonPublisher: CUP Archive
ISBN: 9780521219433
Category : Science
Languages : en
Pages : 430
Book Description
Gas-fluidized Bed Vibration, an Experimental Study
Author: James Francis WelchHandbook of Fluidization and Fluid-Particle Systems
Author: Wen-Ching YangPublisher: CRC Press
ISBN: 0203912748
Category : Science
Languages : en
Pages : 876
Book Description
This reference details particle characterization, dynamics, manufacturing, handling, and processing for the employment of multiphase reactors, as well as procedures in reactor scale-up and design for applications in the chemical, mineral, petroleum, power, cement and pharmaceuticals industries. The authors discuss flow through fixed beds, elutriation and entrainment, gas distributor and plenum design in fluidized beds, effect of internal tubes and baffles, general approaches to reactor design, applications for gasifiers and combustors, dilute phase pneumatic conveying, and applications for chemical production and processing. This is a valuable guide for chemists and engineers to use in their day-to-day work.
Gas Flow in Fluidized Beds of Large Particles
Author: Goran N. JovanovicPublisher:
ISBN:
Category : Fluidization
Languages : en
Pages : 150
Book Description
Gas mixing is studied in fluidized beds of large particles. The bed is 0. 483 m by 0. 127 m (19 in. by 5 in.) in cross section and has transparent plexiglass panels on the front and back. A tube matrix made of twenty-seven 50.8 mm (2 in.) diameter plexiglass cylinders fixed in an equitriangular pitch (with the pitch to diameter ratio equal to 2) is used to study the effects of tubes. Experiments are done in a bed with and without tube array. Sand and dolomite particles with mean particle diameter of 1.3 mm (0. 051 in.) to 4.0 mm (0. 157 in.) are used. Gas velocities are varied from minimum fluidization velocity to an excess velocity of 2.5 m/s. Two large particle fluidization regimes are described. The experimental evidence is presented in support of the existence of slow bubble and exploding bubble regimes. A semi-theoretical equation establishing the boundary between these two modes of fluidization is derived. A slow bubble regime is encountered in the bed in which the interstitital velocity of the gas exceeds the rising velocity of bubbles. Here the gas uses the bubble as a convenient shortcut on its way through the bed. The exploding bubble regime is reached at higher superficial gas velocities when the bubble growth rate is of the same magnitude as the bubble rise velocity. Large pressure drop oscillations, gross gas bypassing, defluidization of some of the particles and rapid bubble growth are characteristics of the exploding bubble regime. A new criterion is suggested for distinguishing between the fast and the slow bubble regimes. The criterion is derived as a relationship between two non-dimensional groups. The expansion of the bed of large particles with and without tube array is also studied. Theoretical equations are proposed for correlating relative bed voidage versus relative excess gas velocity. They are based on the two-phase theory and all are developed as a special case of one general equation. The equation derived for the slow bubble regime fits the experimental data of this study better than other existing correlations. The equation developed for the fast bubble regime compares favorably with literature data for fine particles. A special case of the general equation can be developed for stationary bubbles and for the slugging regime. It is found that there is little difference in expansion of beds with and without a tube array at low excess gas velocities. However, for higher excess gas velocities expansion is considerably greater for beds with a tube array. Exploding bubbles in a bed without tubes are responsible for this difference. The dispersion of tracer gas injected continuously through a line source above the distributor plate is determined for time-averaged concentration measurements. The tracer concentration at points within the bed is successfully predicted using a single-phase model with interstitial gas velocity (based on average bed voidage) as a characteristic fluidization velocity. The model is insensitive to axial dispersion and depends only on radial dispersion coefficients. The radial dispersion coefficient does not depend on either horizontal or vertical position in the bed and is a strong function of excess gas velocity. Considerable difference is found in tracer dispersion in beds with and without tube array. A new model, called the meandering flow model, is proposed for gas flow through fluidized beds of large particles. The concept of meandering flow is developed on the basis of actual physical movement of gas. The series of peaks observed in tracer concentration data records are explained by a bulk lateral movement of gas induced by large bubbles. A simple mathematical technique is suggested for the analysis of tracer data. As a result of the application of the meandering flow model the turbulent and meandering dispersion coefficients are defined. Meandering of fluid through the bed does not contribute to gas mixing, and consequently the meandering dispersion coefficient has to be subtracted from the overall radial dispersion coefficient. Only the turbulent dispersion should be used in the evaluation of the extent of gas mixing in fluidized beds of large particles, which contributes to gas phase combustion.
Advances in Chemical Engineering
Author: Zeeshan NawazPublisher: BoD – Books on Demand
ISBN: 953510392X
Category : Technology & Engineering
Languages : en
Pages : 598
Book Description
Chemical engineering applications have been a source of challenging optimization problems in terms of economics and technology. The goal of this book is to enable the reader to get instant information on fundamentals and advancements in chemical engineering. This book addresses ongoing evolutions of chemical engineering and provides overview to the sate of the art advancements. Molecular perspective is increasingly important in the refinement of kinetic and thermodynamic molding. As a result, much of the material was revised on industrial problems and their sophisticated solutions from known scientists around the world. These issues were divided in to two sections, fundamental advances and catalysis and reaction engineering. A distinct feature of this text continues to be the emphasis on molecular chemistry, reaction engineering and modeling to achieve rational and robust industrial design. Our perspective is that this background must be made available to undergraduate, graduate and professionals in an integrated manner.